1. Field of the Invention
The present invention relates to an inspection apparatus that inspects defects of a pattern formed on a surface of an inspection object, and specifically, to an inspection apparatus that captures secondary charged particles varying properties of a surface of an inspection object, forms image data, and inspects a pattern and the like formed on the surface of the inspection object on the basis of the image data at a high throughput, and an inspection method.
2. Description of the Related Art
A conventional semiconductor inspection apparatus supports a 100 nm design rule and technologies. Samples as inspection objects are wafers, exposure masks, EUV masks, NIL (nanoimprint lithography) masks, and substrates; the samples have thus been varying. At present, apparatuses and technologies that support a design rule for samples with 5 to 30 nm are required. That is, it is required to support L/S (line/space) or hp (half pitch) nodes of 5 to 30 nm in a pattern. In the case where an inspection apparatus inspects such samples, it is required to achieve a high resolution.
Here, “samples” are exposure masks, EUV masks, nanoimprint mask (and templates), semiconductor wafers, substrates for optical elements, substrates for optical circuits and the like. The samples include samples with patterns and samples without patterns. The samples with patterns include samples with asperities and samples without asperities. Patterns are formed of different materials on the samples without asperities. The samples without patterns include samples coated with an oxide film and samples with no oxide film.
Problems of the conventional inspection apparatuses are summarized as follows.
A first problem is insufficient resolution and throughput. In a conventional art of a mapping optical system, the pixel size is about 50 nm, and the aberration is about 200 nm. Achievement of further high resolution and improvement of the throughput require reduction in aberration, reduction in energy width of irradiation current, a small pixel size, and increase in current intensity.
A second problem is that, in the case of SEM inspection, the finer the structure to be inspected, the more serious the throughput problem is. This problem occurs because the resolution of an image is insufficient if a smaller pixel size is not used. These points are caused because the SEM forms an image and inspects defects on the basis of edge contrast. For instance, in the case of a pixel size of 5 nm and 200 MPPS, the throughput is approximately 6 hr/cm2. This example takes a time 20 to 50 times as long as the time of mapping projection. The time is unrealistic for inspection.    Patent Document 1: International Publication No. WO2002/001596    Patent Document 2: Japanese Patent Laid-Open No. 2007-48686    Patent Document 3: Japanese Patent Laid-Open No. H11-132975